Unraveling the GD-1 Stream and Its Mysterious Cocoon: A DESI Perspective

The study by Valluri et al. uses DESI data to confirm a cocoon surrounding the GD-1 stellar stream—a broader, kinematically hotter structure with a common origin. Possible explanations include pre-accretion stripping, debris from a parent galaxy, interactions with dark matter subhalos, or perturbations from the Sagittarius dwarf galaxy. Future DESI observations will help determine the cocoon’s origin, providing insights into the Milky Way’s evolution and dark matter structure.